The world's largest emitter of greenhouse gases is now pushing ahead with plans to develop renewable energy sources.

China is pushing ahead with plans to develop renewable energy sources. At the same time, though, the world's largest emitter of greenhouse gases is still largely reliant on one major source of carbon emissions - coal.

The Asia Society's Orville Schell had an epiphany when he visited heavily polluted Shanxi province a few years ago.

"I knew I was going to be in coal country, but I was shocked by what I saw. And it was at that moment, I felt like St. Paul on the road to Damascus (a Biblical reference to being on the road to truth). The scales [blinders] fell from my eyes and I realized coal is the heart of the matter," said Schell

Coal is the most abundant energy source in China and it generates 70 percent of the nation's power. Greenpeace activist Li Yan says her organization thinks one reason Chinese companies still rely on coal is because coal is "very, very cheap."

"So, a reform in the pricing system of coal, to internalize all the environmental and health damage, and all the external damages, to have it reflect in the real price of coal," she said.

Burning coal emits carbon dioxide, one of the main greenhouse gases that many scientists say contribute to global warming.

Climate change was one of the highlights of recent agreements between China and the United States, the world's two largest emitters of greenhouse gases. During a visit to China in November, President Barack Obama outlined specific ways the two countries have agreed to work together.

"We are creating a joint clean energy research center, and have achieved agreements on energy efficiency, renewable energy, cleaner uses of coal, electric vehicles, and shale gas," he said.

Despite the friendly words, the Copenhagen climate change summit this month underscores the vast difference between the U.S. and Chinese positions. Developed countries think that although China is a developing nation, it should take more proactive steps to fight climate change because it is the world's largest emitter of greenhouse gases.

Yu Qingtai, part of the Chinese delegation to the climate change talks, says China believes in the idea of "common but differentiated responsibilities."

Yu says under this principle, it is not fair to ask developing countries like China and India to take on the same responsibilities as developed countries.

But China's continued development means that as the economy continues to grow, even more coal will be burned and more carbon released into the atmosphere.

This dilemma was underscored by China's recent announcement that it will reduce its carbon intensity by up to 45 percent by 2020, compared with 2005 levels. In other words it will emit less carbon dioxide for each unit of economic output. But that does not reduce China's overall emissions, it only slows the growth.

Chinese people suffer much of the environmental burden brought on by the country's growing coal use, because of thick air pollution, as well as climate change. Several studies have shown that China's chronically dirty air contributes to thousands of illnesses and deaths a year. And pollution increasingly is a social issue driving thousands of Chinese to protest against the government and businesses.

Climate experts say this is why the government cannot ignore the problem.

Wu Changhua is the Greater China director of an international non-profit organization called the Climate Group.

"I think with or without international agreement or not, it's actually happening here already - not just for the meeting at Copenhagen. In the last five years or 10 years, actually, China is already starting to shift to low-carbon development pathway," said Wu.

The problem is enormous, but experts say they see signs that change is possible in China.

Tsinghua University economist Hu Angang says he is encouraged that Chinese officials increasingly talk about the need to pursue so-called green energy and the importance of having a green economy.

"This is good news, a good signal for us, to change our model," said Hu.

Hu acknowledges that an international agreement on climate change is important. But he says for China, reducing emissions - from coal and other sources - is also very much in its own national interest.